Log Message:
devel/garden: update to 1.0.0

v1.0.0
Features
 - Commands can now specify pre-commands and post-commands that are run
   before/after the specified command. (#3) (documentation)
 - The default origin remote name can now be configured using
   tree.<tree>.default-remote. (#16)
 - Commands now display the tree's current branch alongside the tree name. (#18)
 - garden -vv exec and garden -vv shell now display the command being run.

Packaging:
 - garden can now be installed as a nix flake package. A flake.nix file is now
   provided. (#16)